This is a basic FMCW radar simulation example based on RadarSimPy.
RadarSimPyis a radar simulation package built with python. Contact me if you are interested in this module.
This notebook is available on my GitHub.
The following table lists the basic parameters of the radar transmitter.
| Parameter | Variable in RadarSimPy |
Value |
|---|---|---|
| Center frequency ($f_c$) | fc | 24.125 GHz |
| Bandwidth ($B$) | bandwidth | 100 MHz |
| Transmitted power ($P_t$) | tx_power | 10 dBm |
| Rising or falling chirp | slop_type | rising |
| Chirp repetition period ($CRP$) | repetition_period | 100 us |
| Chirp length ($T$) | pulse_length | 80 us |
| Number of chirps | pulses | 256 |
| Chirp start delay | delay | 0 s |
The radiation pattern os the transmitter antenna is $\cos{\theta}$. The gain of the antenna is 6 dB.
import numpy as np
from radarsimpy import Radar, Transmitter, Receiver
angle = np.arange(-90, 91, 1)
pattern = 20 * np.log10(np.cos(angle / 180 * np.pi) + 0.01) + 6
tx_channel = dict(
location=(0, 0, 0),
azimuth_angle=angle,
azimuth_pattern=pattern,
elevation_angle=angle,
elevation_pattern=pattern,
)
tx = Transmitter(fc=24.125e9,
pulse_length=80e-6,
bandwidth=100e6,
tx_power=10,
slop_type='rising',
repetition_period=100e-6,
pulses=256,
channels=[tx_channel])
The parameters of the receiver are listed in the table below.
| Parameter | Variable in RadarSimPy |
Value |
|---|---|---|
| Sampling rate ($f_s$) | fs | 2 Msps |
| Noise figure ($NF$) | noise_figure | 12 dB |
| RF gain/loss ($G_{rf}$) | rf_gain | 20 dB |
| Load resistor ($R_L$) | load_resistor | 500 $\Omega$ |
| Baseband voltage gain ($G_{BB}$) | baseband_gain | 30 dB |
The radiation pattern os the receiver antenna is $\cos{\theta}$. The gain of the antenna is 6 dB.
rx_channel = dict(
location=(0, 0, 0),
azimuth_angle=angle,
azimuth_pattern=pattern,
elevation_angle=angle,
elevation_pattern=pattern,
)
rx = Receiver(fs=2e6,
noise_figure=12,
rf_gain=20,
load_resistor=500,
baseband_gain=30,
channels=[rx_channel])
Create the FMCW radar model based on all the parameters defined above.
radar = Radar(transmitter=tx, receiver=rx, type='FMCW')
Calculate the characteristics of the FMCW radar:
Maximum range (with I/Q baseband): $$R_{max}=\frac{c f_s T}{2B}$$
Maximum range (without I/Q baseband): $$R_{max}=\frac{c f_s T}{4B}$$
Unambiguous velocity: $$v_{ua}=\frac{c}{2 CRP \times f_c}$$ or $$v_{ua}=\pm \frac{c}{4 CRP \times f_c}$$
Range resolution: $$\delta_r=\frac{c}{2B}$$
print('Maximum range: ', radar.max_range, ' m')
print('Maximum unambiguous speed: ', radar.unambiguous_speed, ' m/s')
print('Range_resolution: ', radar.range_resolution, ' m')
The propertities of targets are defined here. There are 3 targets in this simulation. The locations of the targets are defined through $(x, y, z)$ coordinates in meters, and the speeds of the targets are defined trough $(v_x, v_y, v_z)$ in $m/s$. The propertites of the targets also includes radar cross-section (RCS (dBsm)) and phase (radian).
target_1 = dict(location=(0, 200, 0), speed=(0, -5, 0), rcs=20, phase=0)
target_2 = dict(location=(20, 95, 0), speed=(0, -50, 0), rcs=15, phase=0)
target_3 = dict(location=(-5, 30, 0), speed=(0, -22, 0), rcs=5, phase=0)
targets = [target_1, target_2, target_3]
import plotly.graph_objs as go
from plotly.offline import iplot
rx_locations = radar.receiver.locations
tx_locations = radar.transmitter.locations
rx_axis = go.Scatter3d(
x=rx_locations[:, 0],
y=rx_locations[:, 1],
z=rx_locations[:, 2],
mode='markers',
name='Receiver',
marker=dict(color='rgb(17, 157, 255)',
size=8,
opacity=0.8,
symbol='square'),
)
tx_axis = go.Scatter3d(
x=tx_locations[:, 0],
y=tx_locations[:, 1],
z=tx_locations[:, 2],
mode='markers',
name='Transmitter',
marker=dict(color='rgb(233, 30, 99)', size=8, opacity=0.8,
symbol='square'),
)
data = [rx_axis, tx_axis]
for target_idx, target in enumerate(targets):
target_loc = go.Scatter3d(
x=[target['location'][0]],
y=[target['location'][1]],
z=[target['location'][2]],
mode='markers',
name='Target ' + str(target_idx),
marker=dict(size=6, opacity=0.8),
)
data = data + [target_loc]
camera = dict(
up=dict(x=0, y=0, z=1),
center=dict(x=0, y=0, z=0),
eye=dict(x=0, y=-1.5, z=1.8),
)
layout = go.Layout(
title='Radar Scene',
scene=dict(xaxis=dict(title='X (m)'),
yaxis=dict(title='Y (m)'),
zaxis=dict(title='Z (m)'),
camera=camera,
aspectmode='cube'),
margin=dict(l=0, r=0, b=120, t=120),
height=800,
)
fig = go.Figure(data=data, layout=layout)
iplot(fig)
Calculate baseband signal matrix: $$[channel, slow~time, fast~time]$$
import radarsimpy.simulator as sim
data = sim.run_simulator(radar, targets)
timestamp = data['timestamp']
baseband = data['baseband']
data = []
for idx in range(0, 10):
chirp = go.Scatter(
x=timestamp[0, idx, :] * 1e6,
y=np.linspace(
radar.transmitter.fc - radar.transmitter.bandwidth / 2,
radar.transmitter.fc + radar.transmitter.bandwidth / 2,
radar.samples_per_pulse,
endpoint=False,
) / 1e9,
name='Chirp ' + str(idx),
)
data = data + [chirp]
layout = go.Layout(
title='Transmitter chirps',
yaxis=dict(tickformat='.2f', title='Frequency (GHz)'),
xaxis=dict(tickformat='.2f', title='Time (µs)'),
)
fig = go.Figure(data, layout=layout)
iplot(fig)
beat_I = go.Scatter(
x=timestamp[0, 0, :] * 1e6,
y=np.real(baseband[0, 0, :]),
name='I',
)
beat_Q = go.Scatter(
x=timestamp[0, 0, :] * 1e6,
y=np.imag(baseband[0, 0, :]),
name='Q',
)
data = [beat_I, beat_Q]
layout = go.Layout(
title='I/Q Beat Signals for the First Chirp',
yaxis=dict(tickformat='.2f', title='Amplitude (V)'),
xaxis=dict(tickformat='.2f', title='Time (µs)'),
)
fig = go.Figure(data, layout=layout)
iplot(fig)
from scipy import signal
import radarsimpy.processing as proc
range_window = signal.chebwin(radar.samples_per_pulse, at=60)
range_profile = proc.cal_range_profile(radar, baseband, range_window)
temp = np.abs(range_profile[0, :, :])
temp = 20 * np.log10(temp + 0.001)
range_axis = np.linspace(
0, radar.max_range, radar.samples_per_pulse, endpoint=False)
doppler_axis = np.linspace(
0, radar.transmitter.pulses, radar.transmitter.pulses, endpoint=False)
data = [go.Surface(x=range_axis, y=doppler_axis, z=temp, colorscale='Rainbow')]
layout = go.Layout(
title='Range Profile',
height=800,
scene=dict(
xaxis=dict(title='Range (m)'),
yaxis=dict(title='Chirp'),
zaxis=dict(title='Amplitude (dB)'),
aspectmode='cube',
),
margin=dict(l=0, r=0, b=60, t=100),
legend=dict(orientation='h'),
)
fig = go.Figure(data=data, layout=layout)
iplot(fig)
doppler_window = signal.chebwin(radar.transmitter.pulses, at=60)
range_doppler = proc.cal_range_doppler(
radar, range_profile, doppler_window, fft_shift=False)
temp = np.abs(range_doppler[0, :, :])
temp = 20 * np.log10(temp)
range_axis = np.linspace(
0, radar.max_range, radar.samples_per_pulse, endpoint=False)
doppler_axis = np.linspace(
-radar.unambiguous_speed, 0, radar.transmitter.pulses, endpoint=False)
data = [go.Surface(x=range_axis, y=doppler_axis, z=temp, colorscale='Rainbow')]
layout = go.Layout(
title='Range Doppler',
height=800,
scene=dict(
xaxis=dict(title='Range (m)'),
yaxis=dict(title='Velocity (m/s)'),
zaxis=dict(title='Amplitude (dB)'),
aspectmode='cube',
),
margin=dict(l=0, r=0, b=60, t=100),
legend=dict(orientation='h'),
)
fig = go.Figure(data=data, layout=layout)
iplot(fig)